Thank you for the replies.

I have tried both dumping the powder as well as the diluted DE into the skimmer and very slowly. Sometimes I'd notice that there'd be some that go back out through the pool returns, i.e. back into the pool.

That's why I was wondering how people ensure the DE gets applied evenly to the membrane.

Is it normal for some DE to go back into the pool? Or does that mean there's something wrong with the filter or with how it's re-assembled?